File upload conflicts dialog stable5

bakport of the file conflics dialog in https://github.com/owncloud/core/pull/4766 to stable 5.

pulls in some dependencies mostly octemplates, oc-dialogs and their js & css stuff.

had some problem with the breadcrumbs please test them thoroughtly.

I could leave out OC Preview and ajax navigation.

@karlitschek @DeepDiver1975 @MTRichards @kabum @VicDeo @Kondou-ger if you got time to test this evenig would be awesome, then I can fix any bugs tomorrow ... before I am on Vacation for ~three weeks. (will be available partly the last week)

public upload and browser compatibility not yet tested ...